The essence-energies distinction is a doctrine that explains why God is able to be in more than one place at the same time. It's a way to explain how God can be everywhere, all at once.
Essence and energy are two different ways of understanding God. God's essence is His being. It is the way that God is, His qualities and characteristics. Energy, on the other hand, is the way God acts. It's the actions He takes in the world.
Essence and energy work together to help us understand how one God can be in so many different places at once. God's essence stays the same, but His energy can be expressed in different ways. He can create different realities, at the same time, in different places. That's why He can be in multiple places, all at the same time.